Fix #9879: allow top-level opaque type definitions in REPL #32867

Job	Run time
test_scala2_library_tasty	0s
test	56m 3s
test_non_bootstrapped	0s
test_windows_fast	37m 29s
community_build_a	50m 40s
community_build_b	1h 26m 50s
community_build_c	1h 1m 38s
MiMa	12m 58s
test_windows_full	0s
test_java8	0s
test_sbt	22m 17s
build-msi-package	0s
build-sdk-package / build	7m 51s
build-chocolatey-package / build	18s
test-chocolatey-package	0s
publish_nightly	0s
publish_release	0s
nightly_documentation	0s
open_issue_on_failure	0s
	5h 36m 4s

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